Field of the Invention
I. Technical Field
The present invention relates to an engine cooling system, and more particularly to an engine cooling system having an overflow bottle which maintains the cooling system in a pressurized state.
II. Discussion
Engine cooling systems play a critical role in internal combustion engine performance and operation. Primarily, the engine cooling system is responsible for maintaining the engine below a specific temperature by pumping heat, generated by the combustion of fuel within the engine, out to a radiator and ultimately to the atmosphere.
Typical automobile engine cooling systems are known as closed cooling systems. Closed cooling systems circulate a cooling medium, such as an antifreeze-water mixture, through a fully encapsulating circulatory system. This system has the advantage of using the increased temperature within the cooling system to correspondingly increase the pressure. Increased pressure increases the boiling point of the coolant which, as is understood by one skilled in the art, thereby increases the effectiveness of the system in dissipating heat. However, if the temperature of the engine and corresponding cooling medium becomes too high, the pressure within the cooling system will exceed design characteristics and cause damage to the system unless the system is fitted with some means for relieving this pressure. To reduce this pressure buildup, typical cooling systems are fitted with a pressure relieving cap and a reservoir. This cap, typically on the radiator, has a valve which allows pressurized coolant to flow into the tank when the pressure exceeds a specified limit. These check valves typically allow the pressure within the system to build to 14-18 psi before allowing coolant to flow into the tank.
When the engine and corresponding cooling system cools, the pressure within the system drops while the excess coolant remains in the reservoir. When the pressure of the system drops below atmospheric pressure, the difference in pressure between the system and the atmosphere causes coolant within the reservoir to flow back into the cooling system until the pressure equalizes. As a result, anytime the engine and corresponding cooling system is decreasing in temperature, the pressure of the system is usually at or below atmospheric pressure. Low pressure corresponds to a low boiling point temperature which, as discussed above, results in the system having a reduced effectiveness in dissipating heat.
To overcome this drawback, pressurized reservoirs which are maintained at the same pressure as the cooling system and through which a portion of the engine coolant circulates have been developed. These tanks allow the coolant space to expand and contract while maintaining the cooling system at a higher than atmospheric pressure. However, these reservoirs have several drawbacks. First, because of their complexity, typical pressurized reservoirs are rather large, thereby requiring much room in the engine compartment of an automobile. With the ever increasing number of components within an engine compartment, it is difficult to find room for such a tank. Second, again because of their complexity, these reservoirs are expensive. This, too, is an undesirable feature. Third, these reservoirs require at least two additional plumbing circuits to supply coolant to and remove from the reservoir.